Vertical retrace with zoom and centered fast retrace
US5369341A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 11, 1992 |
| Grant date | Nov 29, 1994 |
| Priority date | — |
| Expiry date | Dec 11, 2012 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N3/27
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A television receiver is controlled as to the degree of vertical zoom via a deflection current ramp that varies in slope and which may be delayed to achieve panning. Due to the increased slope when zoomed, the deflection current and the electron beam complete a trace in less time than the normal vertical interval. The deflection current is maintained at one extreme or the other outside the trace interval, and the beam is blanked. A retrace signal generator coupled in a feedback loop with the power supply for the deflection circuit determines the midpoint of the blanking period and generates a fast retrace at or near the midpoint. The feedback loop is arranged to minimize the DC average current in the deflection winding by having a current source responsive to the DC average current for charging a timing ramp that triggers retrace upon reaching a threshold. The slope of the timing ramp varies with DC loading, thus advancing or retarding retrace to center retrace in the blanking interval.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.